Field of the Invention
The present invention relates to a circuit and a method for recording and playing back voice and other sounds in digital mobile radio devices.
In the prior art, in order to store voice in mobile radio devices, the received voice data has hitherto been stored in digital form in a memory. The corresponding voice data has later been called from the memory and played back via the normal receive-end voice decoder of the mobile radio device and its loudspeaker. Voice recorded by the mobile radio device using the built-in microphone has been stored in digital form in the memory by the normal voice encoder after customary digitization, and transmitted from the memory at a later time.
The European patent application EP 0 762 711 A2 describes a dual-band mobile telephone which can be operated in an analog mode and a digital mode. The device also has a memory in which both received voice information and voice information which is to be transmitted can be stored. In this context a suitable circuit ensures that the data stored in the memory are always present in a compressed form. If received voice signals are to be stored in the memory, the demodulated voice signal is fed to the memory either directly (digital mode) or compressed (in analog mode) with a reduced signal rate and then supplied to the memory. The compressed voice data is output to the loudspeaker of the mobile radio device by a voice decoder, and accordingly there is no need for a further voice decoder to transmit the stored voice data via the radio link.
A further prior art is scheme is disclosed in Siemens Firmware Dokumentation [Siemens Firmware Documentation] PMB 2800/2707, pages 121 to 125. This prior art has the following disadvantages:
The data format is dependent on the voice code used and furthermore the data can be stored only in the form in which they were transmitted by radio. Because of the relatively high susceptibility of the radio path to interference, it is usually necessary additionally to provide error correction data which unnecessarily increase the storage capacity required. In addition, it is subsequently impossible to perform further compression of the data record according to the prior art. Furthermore, the prior art does not permit correction of data which have been received with interference and which are to be transmitted after storage.
It is accordingly an object of the invention to provide a method for storing voice in mobile radio devices and a circuit for performing the method which overcomes the above-mentioned disadvantageous of the prior art methods and circuits of this general type, and in which the method is substantially more flexible than prior art methods.
With the foregoing and other objects in view there is provided, in accordance with the invention a circuit for recording and playing back voice and other sounds in digital mobile radio devices. The circuit includes a transmit signal path including a first voice encoder configured therein for encoding voice signals to be transmitted via a radio link; a receive signal path including a first voice decoder configured therein for decoding voice signals received via the radio link; a memory for storing voice signals and for outputting the voice signals; a second voice encoder having an output connected to the memory; and a second voice decoder having an input connected to the memory for receiving the voice signals output from the memory. The second voice decoder is configured for decoding the voice signals output from the memory and for sending the voice signals output from the memory to a loudspeaker. The first voice decoder is configured to always decode ones of the voice signals received via the radio link that are to be stored in the memory and to send the decoded ones of the voice signals to the second voice encoder for subsequent encoding.
This voice storage (frequently also referred to as xe2x80x9cVoice Memoxe2x80x9d will preferably also permit the following functions:
1. The mobile radio device will be used as a dictaphone in the so-called xe2x80x9cstand-byxe2x80x9d mode, i.e. if the device is switched on, without a call being made.
2. It will be possible to output previously recorded messages to the other party or to the original party itself or to both during the call.
3. In addition it should be possible to output different messages to the other party or to the original party itself.
4. Furthermore, it should be possible during the call to record only the other party, only the original party itself or both parties.
As a result, the voice data can be stored in a data format which is more efficient with respect to memory location.
In accordance with an added feature of the invention, the circuit is configured in such a way that the output of the second voice decoder is connected to the loudspeaker of the mobile radio device. In this way playback of the stored data to the user of the mobile radio device is improved.
In accordance with an additional feature of the invention, the circuit is provided with a further, third voice decoder whose input is connected to the memory. Preferably, the output of the third voice decoder is connected to the input of the first voice encoder. This permits very flexible calling of stored messages for transmission.
In accordance with an another feature of the invention, the second voice encoder is connected via a summing point both to the output of the receive-end, first voice decoder and to the microphone of the mobile radio device. In this way, both received messages and messages which are input by the user of the mobile radio device can be stored in a particularly advantageous way.
In accordance with a further feature of the invention, a controllable amplifier is connected between the output of the first voice decoder and the summing point and between the microphone and the summing point, respectively. In this way, both the signal from the original party itself and the signal received from the other party can be stored together during the call.
The controllability of the amplifier also permits very good adaptation of the drive level control.
In accordance with a further added feature of the invention, the connection between the second voice decoder and the loudspeaker is made via a further summing point whose other input is connected to the output of the first voice decoder. It is particularly preferred here to connect a controllable amplifier between the output of the second voice decoder and the further summing point and between the output of the first voice decoder and the further summing point, respectively. In this way, it is also possible to simultaneously play back from the memory and listen to the currently received signal.
In accordance with a further additional feature of the invention, the connection between the third voice decoder and the input of the transmit-end, first voice encoder is made via an additional summing point whose other input is connected to the microphone output. It is particularly preferred here to connect a controllable amplifier between the output of the third voice decoder and the additional summing point and between the microphone output and the additional summing point, respectively. In this way, it is also possible to transmit a previously stored message while simultaneously giving a commentary. The controllable amplifiers again permit suitable drive level control of the two signals.
With the foregoing and other objects in view there is also provided, in accordance with the invention a method for recording and playing back voice and other sounds in digital mobile radio devices in which the voice is transmitted in digitally encoded form and a possibility for storing voice signals is provided. The method includes: transmitting a voice signal in a digitally encoded form via a radio link; always using a method to encode a voice signal to be stored that is independent from a method used to encode the voice signal that is transmitted via the radio link; and always using a method to decode the stored voice signal that is independent from a method used to decode the voice signal that is transmitted via the radio link.
In accordance with a concomitant mode of the invention, the method uses different coding and decoding circuits for the stored voice signals than for the voice signals transmitted via the radio link.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a circuit and method for recording and playing back voice and other sounds in digital mobile radio devices, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.